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Pregnant patients present special challenges in the emergency department

Many pregnant women visit the emergency department (E.D.) when seeking medical care, especially if their condition is unrelated to their pregnancy or they don’t have a primary care physician (PCP). However, according to the February 21, 2015 issue of “Modern Healthcare,” emergency physicians report that they are generally uncomfortable treating pregnant women. The article goes on to mention that, on average, pregnant patients in the E.D. see an obstetrician/gynecologist (OB/GYN) within 45 minutes – higher than the average time for other consults in other areas. Fast consults statistically will increase patient satisfaction and reduce unnecessary admissions. But those 45 minutes can be critical, so there are some things E.D. physicians should keep in mind when treating obstetric patients.

Three systems to pay especially close attention to in pregnant women seeking emergency care are the cardio-vascular, respiratory and renal systems. Below are some important facts to remember about these systems with regard to pregnancy.

Cardio-Vascular System

In terms of blood volume, expect to see an increase in plasma volume by about 45 percent. This increase begins after six to eight weeks of pregnancy and peaks at 32 weeks. Red blood cells may increase by 20 to 30 percent. This can create hemodilution with a decrease in maternal hematocrit. An increase in erythropoiesis should also be expected, with an increase in the erythrocyte concentration levels of two or three diphospho glycerate. This also causes a lower affinity for maternal hemoglobin to oxygen.

Anatomical changes to the cardio-vascular system include an increase in ventricular wall muscle mass and end-diastolic volume without an increase in end-diastolic pressure. Softening of collagen in the vascular system also leads to increased compliance of arteries and veins.

Cardiac output for pregnant women normally increases by 30 to 50 percent. Half of this increase occurs before the eight-week mark. By 32 weeks, there is an increase in the heart rate of 15 to 20 beats per minute. Posture also affects the cardiac output – moving from the left recumbent position to a supine position can cause a drop in cardiac output by 23 to 30 percent. Eight percent of women become symptomatic. The increase in cardiac output is selective, however: the uterus gets 17 percent of the increase at term versus two percent in the non-pregnant state; kidneys, breast and skin receive more of it than in the non-pregnant state; the brain and liver are unchanged.

A decrease in the blood pressure is normal up to 24 to 32 weeks of pregnancy, then it returns to pre-pregnancy levels. Obese women usually have higher blood pressure and lower heart rates during pregnancy and do not show the normal decrease typically seen in the first and second trimesters. A decrease in systemic vascular resistance shows as early as five weeks, secondary to progesterone, prostaglandins and the low resistance uteroplacental circulation.

In terms of antepartum hemodynamics, there is a decrease in colloid osmotic pressure. The pulmonary capillary wedge pressure (PCWP) remains unchanged. These issues put pregnant women at increased risk of developing pulmonary edema.

Post-partum changes include an increased cardiac output of 80 percent within 15 minutes of a vaginal delivery. The left atrial dimension increases one to three days after delivery, secondary to mobilization of excessive body fluids and increased venous return. Atrial natriuretic levels also go up to help with diuresis.

Respiratory System

There is a decrease in the functional residual capacity secondary to a decrease in expiratory reserve volume and residual volume, all of which is secondary to the upward displacement of the diaphragm. Tidal volume increases by 40 percent. This increase combined with an unchanged respiratory rate causes maternal hyperventilation and hypocapnea. Normal carbon dioxide partial pressure (PCO2) levels in pregnancy are 28 to 31 millimeters of mercury (mm Hg) versus 39 mm Hg in the non-pregnant state. This helps transfer carbon dioxide (CO2) from fetus to mother.

Pregnant women have a mild respiratory alkalosis – 7.44 versus 7.40. There is also an increase in maternal oxygen consumption of 20 to 40 percent. This, along with a decrease in functional residual capacity, can lead to early decompensation in women with respiratory pathology. Oxygen partial pressure (PO2) in pregnant women should be kept above 70 to 80 mm Hg for both fetal and maternal reasons.

Renal System

In pregnancy, kidney volume increases by 30 percent. There is both caliceal and ureteral dilation, with the right more dilated than the left. The GFR is 50 percent compared to the non-pregnant state. This leads to levels of creatinine and blood/urea/nitrogen (BUN) that are lower than normal: creatinine of 0.8 milligrams (mg) per deciliter (dL) versus 0.5 mg/dL and BUN of 12 mg/dL versus 10 mg/dL. There is an increase in sodium retention secondary to changes in the renin-angiotensis-aldosterone system causing water to be retained. This increase leads to changes in sodium osmolality levels – sodium increases 140 millimolar per liter (mM/L) versus 136 mM/L and osmolality of 289 versus 280.9.

These are just some of the basic alterations in physiology that are associated with normal pregnancies. Calling for an OB/GYN is always wise, even if it’s just to help allay the mothers’ concerns about her fetus.

This article is part one in a series. The continuations will address some common medical disorders that occur during pregnancy such as asthma, pneumonia and deep vein thrombosis.

Adolfo Gonzalez-Garcia is the obstetrical director of both the Regional Perinatal Intensive Care Center and the Broward Health Medical Center in Fort Lauderdale.